Process for producing an embossing cylinder

ABSTRACT

A cylinder is provided with a photographic emulsion which is then exposed to light as a function of a desired pattern. Portions of the exposed emulsion are removed from the cylinder as a function of the exposure obtained in the step of exposing the emulsion to light. The bared portions of the cylinder are then electroplated to provide lands as a function of a pattern to be embossed onto articles.

nited States Patent [191 math et al.

[4 1 Nov. 27, 1973 PROCESS FOR PRODUCING AN EMBOSSING CYLINDER [75] Inventors: Jean Jaques Rieth; Francois Castejon, both of Venissieux, France [73] Assignee: Les Etablissements Marechal S.A.,

Paris, France 22 Filed: Mar. 3, 1971 21 Appl. No.: 120,607

[30] Foreign Application Priority Data Mar. 5, 1970 France 7007853 [52] U.S. Cl 204/15, 101/25, 101/28, 204/25 [51] Int. Cl. C23b 5/48, C23b 5/56 [58] Field of Search 204/17, 25, 15; 101/25, 28, 31; 156/14 [56] References Cited UNITED STATES PATENTS 1 H1948 Bohlmarl et al 204/25 1/1967 Nalband et al. 29/183.5

1,151,459 8/1915 Hatt 204/17 2,024,086 12/1935 Ballard 204/17 2,726,200 12/1955 Holsapple 204/17 3,293,156 12/1966 Allison 204/17 FOREIGN PATENTS OR APPLICATIONS 75,985 9/1954 Netherlands 204/17 OTHER PUBLICATIONS Two New Photo Resists, Photo Methods for Industry Vol. 12 No. 10 Oct. 1969 pgs. 64, 66, 68.

Primary ExaminerThomas Tufariello Attarney-Spencer & Kaye [5 7] ABSTRACT A cylinder is provided with a photographic emulsion which is then exposed to light as a function of a desired pattern. Portions of the exposed emulsion are removed from the cylinder as a function of the exposure obtained in the step of exposing the emulsion to light. The bared portions of the cylinder are then electroplated to provide lands as a function of a pattern to be embossed onto articles.

4 Claims, 13 Drawing Figures IAIENIEIIIIUI 27 I975 3.775.261 SHEET 35? 3 PATTERN I. MAKING PHOTOGRAPHIC 3.

NEGATIVE FILM OF TURNING COPPERED CYLINDER EXPOSURE 2. MAKING POSITIVE FILM I BY STEP AND REPEAT L4. POLISHING GYLINOEH 5. COATING CYLINDER WITH PHOTOSENSITIVE LAYER I6 ENCIRCLING CYLINDER SURFACE WITH POSITIVE FILMW ELIMINATING NONEXPOSED PORTIONS OF PHOTOSENSITIVE LAYER CHEMICALLY ATTACKING BARED SURFACE PORTIONS REINFORCING EXPOSED PORTIONS OF PHOTOSENSITIVE LAYER WITH PROTECTIVE COATING ELECTRODEPOSITING COPPER LANDS ON BARED SURFACE PORTIONS PHOTOSENSITIVE LAYER REMOVING PROTECTIVE COATING AND EXPOSED PORTIONS OF CHROMEPLATING ENTIRE CYLINDER INVENTORS, Jean Jacques RieTh Francois Cosrejon ATTORNEYS.

I PROCESS FOR PRODUCING AN EMBOSSING CYLINDER BACKGROUND OF THE INVENTION The present invention relates to a process for fabricating an embossing cylinder useful for embossing decorative patterns onto films of plastic material, to the cylinder itself, and to a process of using the cylinder.

Heretofore, several techniques have been used for l producing embossing cylinders. According to a first technique, a smooth cylinder is machined to provide grooves and lands corresponding to a desired pattern. This process is generally suitable only for the reproduction of geometric designs having small dimensions. A high accuracy is not possible. However, the designs can be placed in very regular arrays. Highly trained machinists must be used; otherwise smooth surface finishes can not be reliably achieved.

According to a second technique, the desired pattern is reproduced'on a cylinder by the electrodeposition of nickel on a form made of plastic. A problem associated with this'process is a poor closure of the pattern.

According to athrid technique, the grooves of a pattern are produced by photoengraving. To this end, a negative of the desired pattern is reproduced on a photosensitive layer previously deposited on a cylinder. After development and elimination of the nonexposed parts of the layer, the surface of the cylinder is subjected to a chemical attack. This process is little utiliz'ed, since the grooves are of shallow depth. Furthermore, the pattern is not faithfully reproduced, and the edges of the lands are sharp and cause tearing and preforating of plastic films being embossed.

SUMMARY OF THE INVENTION An object of the present invention, therefore, is to provide a new and improved process for fabricating an embossing cylinder, which process yields an accurate placement of a desired pattern onto a cylinder.

Another object of the invention is to provide a process yielding lands and grooves having smooth surfaces yet not requiring skilled machinists.

Another object of the invention is to provide aprocess yielding lands which do not cut and tear an article being embossed and which are adequately elevated from the grooves to yield excellent embossing results.

' Yet another object of the invention is to provide a new and improved embossing cylinder and a process of using such a cylinder.

These as well as other objects which will become apparent in the discussion that follows are achieved, according to the present invention, by first photographically providing bared and covered portions on a cylinder and then electrodepositing metal lands on the bared portions.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to are sections through a portion of the surface of a cylinder, with the axis of the cylinder lying in the planes of the sections.

FIG. 111 is a perspective view showing the cylinder of the invention in use.

FIGS. 12 and 13 are flow diagrams of two embodiments of the process of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to one preferred embodiment of the invention, whose essential course is set forth in FIG. 12, a decorative pattern is first selected. This may be a drawing, or it may be a natural design occurring on some object such as a piece of marble, fabric, leather, etc.., A photographic negative film is made of the se- 0 lected pattern. The size of the film may be chosen to have a length equal to l/n times the circumferential length of the cylinder, where n is an integer, so that the positive film made as described below will close correctly on itself. The negative film may be retouched by standard methods.

Next, a larger positive film is produced by successive exposures of the original negative on a step and repeat machine, for example of the Bouzard type. The layout of the larger film should correspond exactly to the layout desired on the surface of the cylinder. This larger film may be retouched, for example, to remove any mismatch occurring at the borders between separate exposures of the original negative and at the two edges of the larger film that must close on themselves in the finished pattern on the cylinder.

The cylinder is of steel having a coppered surface. The surface is turned on a lathe for the purpose of making it perfectly cylindrical and for bringing it to a1diameter such that its surface can be covered exactly by the positive film. Then the surface is carefully polished.

Referring to FIG. I, the polished surface of cylinder l is then coated with a photosensitive layer 2. Portions of this layer which have been'exposed to light must not dissolve in subsequently used solutions such as the iron perchloride solution mentioned below. Otherwise, its particular composition is unimportant. An example of a suitable layer material is Kodak KIR emulsion.

The cylinder is next placed on a Mettenheimer' copying machine with the larger positive film closing upon itself around the cylinder and in contact with-the emulsion and, by means of a powerful light source, for example a xenon lamp a latent image is formed on the photosensitive layer 2. The positive film is removed,

and the image is developed to eliminate the photosensitive layer at the nonexposed portions 4 while maintaining the layer at the exposed portions 3, as shown in FIG. 2.

The image thus obtained on the cylinder can then, if necessary, be retouched either by scraping away unwanted parts of portions 3 or by providing a coating onto bared surface at portions 4.

The bared surface portions are next cleaned, for example by means of a cotton pad impregnated with a solution having a composition: one part by weight sodium dichromate, (Na Cr O two parts by wieght 66Be sulfuric acid, and eight parts by weight water. Following this, the surface is rinsed thoroughly.

The bared surface regions are next subjected to a chemical attack to effect a better adherence of the metal to be subsequently electroplated on such bared regions. To this end, the cylinder is rotated in a solution of 36Be iron perchloride (FeCl for 5. minutes. Inthis way, the bared surface regions are attacked to a depth of the order to 0.02 to 0.04 millimeters, as shown in FIG. 3. This is followed by a thorough rinsing of the cylinder. The above cleaning step can also be repeated, followed by a thorough rinsing and drying.

Before proceeding to the electrolytic deposition of metal onto bared surface portions of the cylinder, it is advantageous to reinforce the exposed portions 3. Referring to FIG. 4, protective coating is shown covering portions 3. Coating 5 must be of a material that is nonconductive and does not disslove, for instance, in the elegtroplating bath. Otherwise, its particular composition is unimportant. A suitable coating material is coating ST 90 020 sold by the Societe de Produits Chimiques de Parnasse de Paris. The coating 5 is applied using a lathe and a leather (flesh side) roller. It is allowed to dry for several hours.

Copper is then electrodeposited on the bared surface portions in a thick coppering tank. Before commencing current flow, the cylinder is first rotated for about five minutes in the 25 to 30C bath in the tank. Then current is allowed to flow through the cylinder as cathode with a current density of 4 amperes per square decimeter of bared wetted surface. The bath composition is 230 grams of copper sulfate (CuSO and 50 grams of sulfuric acid per liter of water.

With the current flowing, the bared surface portions become filled with copper lands 6, as shown in FIG. 5, at locations reproducing the desired pattern.

When the lands have grown to just protrude over the coating 5, the electrodeposition should be stopped, since otherwise the lands will grow laterally over the coating 5 and connect up with their adjoining lands. The closer the adjoining lands, the faster this interconnecting can occur. The height of the lands is thus limited by the fineness of the decorative pattern. For a fine pattern, land heights would be of the order of 0.1 millimeter,'while for a coarser pattern heights as great as 0.3 to 0.4 millimeters can be attained.

Following the electrolytic deposition, the cylinder is thoroughly washed and then dried.

Lands of different heigths can be obtained by selective masking at different times during the electrodeposition process.

rounded ridge. In such cases as shown in FIG. 7, the

electrodeposition can be halted and the ridges coated with a protective varnish 8, such as above-mentioned coating ST 91 020, whence the electrodepositing is recommenced in order to fill the craters by a new deposit of metal 9.

After electrodeposition, the protective coating 5 is removed by washing with solvent-naphtha and the portions 3 are removed by washing in trichloroethylene, to obtain the structure shown in FIG. 8.

Finally, as shown in FIG. 9, the cylinder is given continuous chrome plate by electroplating in a bath having the composition 250 grams of chromic acid and 2.5 grams of sulfuric acid per liter of water. A current density of 25 amperes per square decimeter is used.

There is thus obtained as a final product an embossing cylinder 1 whose lands 6 reproduce a desired pattern.

In an'alternative embodiment, the relief of the cylinder surface is reinforced by first coating the surface of the lands of FIG. 8 with a coating 12, as shown in FIG. 10. This coating may be the above-mentioned coating ST 91 020. After drying, the cylinder is subjected for 6 to 7 minutes to chemical attack by a 36 Be iron perchloride solution. This creates actual grooves 13 in the surface of the cylinder, as contrasted to the relative grooves present in the structure of FIG. 8. After this attack, the cylinder is thoroughly rinsed and coating 12 is removed. The cylinder is then chromed as in FIG. 9.

In another embodiment according to the invention, whose essential course is set forth in FIG. 13, the photosensitive layer 2 of FIG. 1 is encircled by a negative film, rather than a positive film. In this case, after development of the image and removal of the nonexposed portions of the layer, the bared surface portions are chemically attacked to a depth of 0.02 to 0.04 millimeters with iron perchloride and then protected with a wax. Then the light-exposed portions of the photosensitive layer are removed to form new bared surface portions on the cylinder surface and copper lands are electrodeposited on the thus newly bared surface portions in the manner explained above. The steps following step number 13 in FIG. 13 are the equivalents of steps 10 to 14 in FIG. 12.

The process according to the invention permits the attainment, by a simple and inexpensive process, of embossing cylinders which are perfectly cylindrical and which exhibit the high degree of accuracy characteristic of photographic locations in the placement of the lands reproducing the desired pattern.

Referring to FIG. 8, the lands 6 have rounded edges 25 and this permits embossing without fear of cutting or tearing. Embossed products are given a very soft appearance. Nevertheless, the peaks 26 of the lands are very flat, as is also shown in FIG. 9, and this permits the making of embossed sheets having very flat embossed depressions whose reverse sides can be subsequently successfully printed upon.

Finally, embossed patterns having different depths are possible, and, since a single land can be formed with several different heights by the masking process described above, an embossed sheet having different depths in any given depression is possible.

FIG. 11 illustrates a method of using a cylinder 1 made according to the invention. The cylinder is rotatably mounted on the ends of arms 15a and 15b, while arms 15a and 15b are pivoted to swing downwardly at points 16a and 16b. Springs 17a and 17b urge the cylinder 1 with force against thermoplastic film l8 interposed between cylinder 1 and hard-rubber coated backup roll 19. Film 18 is continuously fed from roll 20, in the unembossed state, through the nip 21, and thence, in the embossed state, onto roll 22. At the nip, lands 6 produce depressions 24. Infrared radiator 23 heats cylinder 1 so that it is continually maintained at a temperature appropriate for embossing the film 18.

The phrase accuracy characteristic of a photographic locating process means that points in a pattern formed by lands on the surface of a cylinder are located within a tolerance of i 0.02 millimeters.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

We claim:

1. A process for producing an embossing cylinder having a predetermined pattern, comprising the steps of: placing a photosensitive layer on the surface of a cylinder; exposing portions of the layer to light as a representation of the predetermined pattern; removing portions of said layer as a function of the exposure obtained in said step of exposing, thus forming bared portions of said surface representing the predetermined pattern; chemically attacking said bared portions preparatory to electrodepositing metal onto said bared portions for modifying the surface at such bared portion so as to improve the adherence of such metal to said bared portions; electrodepositing such metal onto said bared portions to form lands of electro-deposited metal all of which protrude above the surface of the cylinder and which conform to the predetermined pattern and removing the remainder of said layer to expose the surface of said cylinder.

2. A process as claimed in claim 1, further compris- 4. A process as claimed in claim 1, wherein the portions removed in said step of removing are those por' tions which are exposed to light in the step of exposing. k 

2. A process as claimed in claim 1, further comprising the step of subjecting the surface of the cylinder between the lands to chemical attack so as to change the relative grooves resulting from the step of electro-depositing into actual grooves.
 3. A process as claimed in claim 1, wherein the portions removed in said step of removing are those portions which are not exposed to light in the step of exposing.
 4. A process as claimed in claim 1, wherein the portions removed in said step of removing are those portions which are exposed to light in the step of exposinG. 